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abstraction

A term in a notational system or other information artifact that is defined with reference to the primitive concepts of the system, or with reference to other abstractions that are ultimately defined by primitives. It is frequently used to aggregate many instances, so that all can be manipulated by a single action; thus, a heading style is a typical word-processor abstraction defined in terms of font properties, and all its instances can be altered by altering its definition.

abstraction hierarchy

A hierarchical description of the functional structure of a work domain, in which work-domain purposes are related to underlying physical structures. Also referred to as a structuralmeans-ends hierarchy because links between adjacent levels connect ends (upper nodes) to means (lower nodes).

ACT-RPM

The latest in a series of computational cognitive architectures developed by John Anderson and colleagues. ACT-RPM contains architectural mechanisms for cognitive, perceptual, and motor performance and learning. It was one of the architectures reviewed in Pew & Mavor (1998). More information about this series of architectures can be found in Anderson (1976, 1983, 1993) and Byrne & Anderson (2001).

actions

A lower level of organization in human endeavor, including simple gestures and other motor behavior.

activity

The significant and typically collective endeavors of humans. It is the fundamental concept in activity theory, which conceives of activity as conducted through individual actions and mediated by artifacts. In the cognitive-dimensions framework, an activity is likewise a significant endeavor conducted through individual actions, but six generic types of activity are distinguished (e.g., search, design, etc.); at present, only individual interaction with information artifacts is considered.

adaptationism, adaptationist approach

The thesis that selection pressures have been the most powerful cause of evolution; a useful methodological heuristic is to assume that biological and behavioral structures are the results of adaptation to the environment.

affordance

Perceptual characteristics of an object that make it obvious what the object can do and how it can be manipulated.

affordances

According to the theory of James J. Gibson, these are directly perceived possibilities for action in the environment.

analog representations

Representations that share the structure of the things they represent. For example, a picture is an analog representation. See also propositional representations.

analytic evaluation

usability evaluation based on a careful analysis or theoretical modeling of user interface features, usually carried out by usability experts